gold/layout.h

   1 // layout.h -- lay out output file sections for gold  -*- C++ -*-
   2
   3 #ifndef GOLD_LAYOUT_H
   4 #define GOLD_LAYOUT_H
   5
   6 #include <list>
   7 #include <string>
   8 #include <utility>
   9 #include <vector>
  10
  11 #include "options.h"
  12 #include "workqueue.h"
  13 #include "object.h"
  14 #include "stringpool.h"
  15
  16 namespace gold
  17 {
  18
  19 class Input_objects;
  20 class Symbol_table;
  21 class Output_section;
  22 class Output_section_symtab;
  23 class Output_section_headers;
  24 class Output_segment;
  25 class Output_data;
  26 class Target;
  27
  28 // This task function handles mapping the input sections to output
  29 // sections and laying them out in memory.
  30
  31 class Layout_task_runner : public Task_function_runner
  32 {
  33  public:
  34   // OPTIONS is the command line options, INPUT_OBJECTS is the list of
  35   // input objects, SYMTAB is the symbol table, LAYOUT is the layout
  36   // object.
  37   Layout_task_runner(const General_options& options,
  38                      const Input_objects* input_objects,
  39                      Symbol_table* symtab,
  40                      Layout* layout)
  41     : options_(options), input_objects_(input_objects), symtab_(symtab),
  42       layout_(layout)
  43   { }
  44
  45   // Run the operation.
  46   void
  47   run(Workqueue*);
  48
  49  private:
  50   Layout_task_runner(const Layout_task_runner&);
  51   Layout_task_runner& operator=(const Layout_task_runner&);
  52
  53   const General_options& options_;
  54   const Input_objects* input_objects_;
  55   Symbol_table* symtab_;
  56   Layout* layout_;
  57 };
  58
  59 // This class handles the details of laying out input sections.
  60
  61 class Layout
  62 {
  63  public:
  64   Layout(const General_options& options);
  65
  66   // Given an input section named NAME with data in SHDR from the
  67   // object file OBJECT, return the output section where this input
  68   // section should go.  Set *OFFSET to the offset within the output
  69   // section.
  70   template<int size, bool big_endian>
  71   Output_section*
  72   layout(Object *object, const char* name,
  73          const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
  74
  75   // Return the Stringpool used for symbol names.
  76   const Stringpool*
  77   sympool() const
  78   { return &this->sympool_; }
  79
  80   // Return whether a section is a .gnu.linkonce section, given the
  81   // section name.
  82   static inline bool
  83   is_linkonce(const char* name)
  84   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
  85
  86   // Record the signature of a comdat section, and return whether to
  87   // include it in the link.  The GROUP parameter is true for a
  88   // section group signature, false for a signature derived from a
  89   // .gnu.linkonce section.
  90   bool
  91   add_comdat(const char*, bool group);
  92
  93   // Finalize the layout after all the input sections have been added.
  94   off_t
  95   finalize(const Input_objects*, Symbol_table*);
  96
  97   // Return the TLS segment.
  98   Output_segment*
  99   tls_segment() const
 100   { return this->tls_segment_; }
 101
 102   // Write out data not associated with an input file or the symbol
 103   // table.
 104   void
 105   write_data(Output_file*) const;
 106
 107   // The list of segments.
 108
 109   typedef std::vector<Output_segment*> Segment_list;
 110
 111   // The list of sections not attached to a segment.
 112
 113   typedef std::list<Output_section*> Section_list;
 114
 115   // The list of information to write out which is not attached to
 116   // either a section or a segment.
 117   typedef std::list<Output_data*> Data_list;
 118
 119  private:
 120   Layout(const Layout&);
 121   Layout& operator=(const Layout&);
 122
 123   // Mapping from .gnu.linkonce section names to output section names.
 124   struct Linkonce_mapping
 125   {
 126     const char* from;
 127     int fromlen;
 128     const char* to;
 129   };
 130   static const Linkonce_mapping linkonce_mapping[];
 131   static const int linkonce_mapping_count;
 132
 133   // Find the first read-only PT_LOAD segment, creating one if
 134   // necessary.
 135   Output_segment*
 136   find_first_load_seg();
 137
 138   // Set the final file offsets of all the segments.
 139   off_t
 140   set_segment_offsets(const Target*, Output_segment*);
 141
 142   // Set the final file offsets of all the sections not associated
 143   // with a segment.
 144   off_t
 145   set_section_offsets(off_t);
 146
 147   // Create the output sections for the symbol table.
 148   void
 149   create_symtab_sections(int size, const Input_objects*, Symbol_table*, off_t*,
 150                          Output_section** osymtab,
 151                          Output_section** ostrtab);
 152
 153   // Create the .shstrtab section.
 154   Output_section*
 155   create_shstrtab();
 156
 157   // Create the section header table.
 158   Output_section_headers*
 159   create_shdrs(int size, bool big_endian, off_t*);
 160
 161   // Return whether to include this section in the link.
 162   template<int size, bool big_endian>
 163   bool
 164   include_section(Object* object, const char* name,
 165                   const elfcpp::Shdr<size, big_endian>&);
 166
 167   // Return the output section name to use for a linkonce section
 168   // name.
 169   static const char*
 170   linkonce_output_name(const char* name);
 171
 172   // Create a new Output_section.
 173   Output_section*
 174   make_output_section(const char* name, elfcpp::Elf_Word type,
 175                       elfcpp::Elf_Xword flags);
 176
 177   // Return whether SEG1 comes before SEG2 in the output file.
 178   static bool
 179   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 180
 181   // Map from section flags to segment flags.
 182   static elfcpp::Elf_Word
 183   section_flags_to_segment(elfcpp::Elf_Xword flags);
 184
 185   // A mapping used for group signatures.
 186   typedef Unordered_map<std::string, bool> Signatures;
 187
 188   // Mapping from input section name/type/flags to output section.  We
 189   // use canonicalized strings here.
 190
 191   typedef std::pair<const char*,
 192                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 193
 194   struct Hash_key
 195   {
 196     size_t
 197     operator()(const Key& k) const;
 198   };
 199
 200   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 201
 202   // A comparison class for segments.
 203
 204   struct Compare_segments
 205   {
 206     bool
 207     operator()(const Output_segment* seg1, const Output_segment* seg2)
 208     { return Layout::segment_precedes(seg1, seg2); }
 209   };
 210
 211   // A reference to the options on the command line.
 212   const General_options& options_;
 213   // The index of the last output section.
 214   unsigned int last_shndx_;
 215   // The output section names.
 216   Stringpool namepool_;
 217   // The output symbol names.
 218   Stringpool sympool_;
 219   // The list of group sections and linkonce sections which we have seen.
 220   Signatures signatures_;
 221   // The mapping from input section name/type/flags to output sections.
 222   Section_name_map section_name_map_;
 223   // The list of output segments.
 224   Segment_list segment_list_;
 225   // The list of output sections which are not attached to any output
 226   // segment.
 227   Section_list section_list_;
 228   // The list of sections which require special output because they
 229   // are not comprised of input sections.
 230   Data_list special_output_list_;
 231   // A pointer to the PT_TLS segment if there is one.
 232   Output_segment* tls_segment_;
 233 };
 234
 235 // This task handles writing out data which is not part of a section
 236 // or segment.
 237
 238 class Write_data_task : public Task
 239 {
 240  public:
 241   Write_data_task(const Layout* layout, Output_file* of,
 242                   Task_token* final_blocker)
 243     : layout_(layout), of_(of), final_blocker_(final_blocker)
 244   { }
 245
 246   // The standard Task methods.
 247
 248   Is_runnable_type
 249   is_runnable(Workqueue*);
 250
 251   Task_locker*
 252   locks(Workqueue*);
 253
 254   void
 255   run(Workqueue*);
 256
 257  private:
 258   const Layout* layout_;
 259   Output_file* of_;
 260   Task_token* final_blocker_;
 261 };
 262
 263 // This task handles writing out the global symbols.
 264
 265 class Write_symbols_task : public Task
 266 {
 267  public:
 268   Write_symbols_task(const Symbol_table* symtab, const Target* target,
 269                      const Stringpool* sympool, Output_file* of,
 270                      Task_token* final_blocker)
 271     : symtab_(symtab), target_(target), sympool_(sympool), of_(of),
 272       final_blocker_(final_blocker)
 273   { }
 274
 275   // The standard Task methods.
 276
 277   Is_runnable_type
 278   is_runnable(Workqueue*);
 279
 280   Task_locker*
 281   locks(Workqueue*);
 282
 283   void
 284   run(Workqueue*);
 285
 286  private:
 287   const Symbol_table* symtab_;
 288   const Target* target_;
 289   const Stringpool* sympool_;
 290   Output_file* of_;
 291   Task_token* final_blocker_;
 292 };
 293
 294 // This task function handles closing the file.
 295
 296 class Close_task_runner : public Task_function_runner
 297 {
 298  public:
 299   Close_task_runner(Output_file* of)
 300     : of_(of)
 301   { }
 302
 303   // Run the operation.
 304   void
 305   run(Workqueue*);
 306
 307  private:
 308   Output_file* of_;
 309 };
 310
 311 } // End namespace gold.
 312
 313 #endif // !defined(GOLD_LAYOUT_H)